D-SLR: Digital Single Lens Reflex Camera. The stuff the professional photographers use. If you are planning to take your love of photography to the next level or you make a living through the camera lens, then this is for you. The lens is detachable so that you can select from a wide range of lenses. You will find a lens for every occasion.
Mirror Less: Lack of optical viewfinder makes it slightly lighter than a D-SLR. The lenses are detachable, just like D-SLR.
Advanced Point and Shoot: Also known as Bridge cameras. They fall in a category between the D-SLRs and Point and Shoot Cameras. These cameras are best for people who are just stepping into the world of photography as most of these models have both manual and automatic photography modes. The lens is non-detachable but has higher optical zoom than a point and shoot camera. So you can get both telephoto and macro effect on the same camera. These are lighter than the previously discussed categories.
Point and Shoot: Basic camera models. If you are looking for a camera to capture your personal moments, which is lighter and easy to maintain, then this is for you. These cameras have limited capabilities with a non-detachable lens. These are the lightest and cheapest of all the above categories.